Tree light availability:FAB 1 : Forests and Biodiversity Experiment - High density diversity

A forest biodiversity experiment (FAB) focused on trees of our region investigates the consequences of multiple dimensions of tree diversity for soil, food webs, plant communities and ecosystems. FAB is designed to unravel effects of three forms of biological diversity: species richness (SR), functional diversity (FD), and phylogenetic diversity (PD). We define FD as the representation of multiple traits of leaves, roots, seeds, and the whole organism that are correlated with species positions along gradients of resource supply, growth, and decomposition. PD is the representation of evolutionary lineages measured as the genetic distances between species. While PD and FD are often correlated, convergent evolution and adaptive differentiation can decouple them. When functional traits that drive specific ecosystem functions are not phylogenetically conserved, PD and FD may give contrasting predictions. SR, PD, and FD are not independent, and we posit that PD may help explain SR effects, and FD may help explain both PD and SR effects. Thus FAB is designed to examine the separate and combined effects of all three components of diversity for multiple ecosystem functions and to distinguish between ???sampling??? and ???complementarity??? effects of biodiversity. Due to the long lag between planting tree seedlings and determining effects of tree composition and diversity on ecosystem functioning, fewer experiments have been established to elucidate the role of biodiversity in the functioning of forest ecosystems than grassland experiments. FAB will contribute to this gap and is a member of the IDENT and TreeDiv network of forest biodiversity experiments (www.treedivnet.ugent.be).

Hypotheses:
1. PD, FD, and SR will all contribute to increased productivity, stability, and diversity of other trophic levels (herbivores, predators, parasitoids, soil microbes, soil flora and fauna) as well as to greater soil C sequestration.
2. Because PD incorporates both the number of species and measurement of their evolutionary divergence, PD will explain more of the variation in ecosystem productivity and stability than SR. Similarly, among-species FD will explain more variation in these ecosystem functions than SR or PD.
3. Plant assemblages of similar SR but comprised of increasingly divergent PD or FD will show increasing divergence in ecosystem functions.
4. Species with functional traits not yet present in a plot will more easily invade than species with traits similar to the established species.

The FAB single species plots will allow us to test hypotheses about the importance of plant functional traits in influencing ecosystem properties (e.g., NPP, soil C, N mineralization) and plant-associated microbial communities. For example, we expect that plant species that increase concentrations of polyvalent soil cations (e.g., because of unique base cation chemistry or because of effects on soil acidity that influence Al and Fe solubility) will promote soil C stabilization through mineral-organic matter interactions and the formation of microaggregates that protect soil C from decomposition.

森林生物多样性实验（FAB）聚焦本区域树木，旨在探究树木多样性多维度特征对土壤、食物网、植物群落及生态系统的影响。FAB旨在解析三类生物多样性的效应：物种丰富度（Species Richness, SR）、功能多样性（Functional Diversity, FD）以及系统发育多样性（Phylogenetic Diversity, PD）。我们将功能多样性定义为涵盖叶片、根系、种子及全株的多重功能性状，这些性状与物种沿资源供给、生长及分解梯度的分布位置密切相关。系统发育多样性则指以物种间遗传距离为衡量标准的演化支系表征。尽管系统发育多样性与功能多样性通常存在相关性，但趋同演化与适应性分化可使二者脱耦。当驱动特定生态系统功能的功能性状不具有系统发育保守性时，系统发育多样性与功能多样性可能会给出相悖的预测结果。物种丰富度、系统发育多样性与功能多样性三者并非独立，我们推测系统发育多样性可辅助阐释物种丰富度的效应，而功能多样性则可同时阐释系统发育多样性与物种丰富度的效应。因此FAB旨在探究三类多样性组分对多种生态系统功能的单独及联合效应，并区分生物多样性的"取样效应"与"互补效应"。由于从种植林木幼苗到明确林木组成与多样性对生态系统功能的效应存在较长时滞，相较于草地生态系统实验，针对森林生态系统生物多样性作用的已建立实验相对较少。FAB旨在填补这一研究空白，同时它隶属于森林生物多样性实验网络IDENT与TreeDiv（网址：www.treedivnet.ugent.be）。

研究假说：
1. 系统发育多样性、功能多样性与物种丰富度均有助于提升生态系统生产力、稳定性以及其他营养级（植食动物、捕食者、寄生性天敌、土壤微生物、土壤动植物）的多样性，同时可增强土壤碳固存能力。
2. 由于系统发育多样性同时涵盖物种数量与物种演化分化程度的测量，相较于物种丰富度，系统发育多样性可更好地解释生态系统生产力与稳定性的变异。同理，种间功能多样性相较于物种丰富度或系统发育多样性，可更好地解释上述生态系统功能的变异。
3. 物种丰富度相似但系统发育多样性或功能多样性梯度递增的植物群落，其生态系统功能的差异程度将随之增大。
4. 携带样地内未出现的功能性状的物种，相较于携带与定居物种相似性状的物种，更易完成入侵。

FAB设置的单物种植被样地，将帮助我们验证关于植物功能性状对生态系统属性（例如净初级生产力（Net Primary Productivity, NPP）、土壤碳、氮矿化作用）及植物关联微生物群落的影响重要性的相关假说。例如，我们推测可提升土壤多价阳离子浓度的植物物种（例如因独特的碱基阳离子化学特征，或通过影响土壤酸度进而改变铝与铁的溶解度），可通过矿物-有机质相互作用以及形成保护土壤碳免于分解的微团聚体，促进土壤碳固持。